Biological tissue elasticity measurement method and ultrasonographic device

ABSTRACT

An ultrasonographic apparatus includes: an ultrasonic probe  1  for transmitting/receiving an ultrasonic wave to/from a patient, means  2  for generating an ultrasonic transmission signal and transmitting it to the ultrasonic probe, means  3  for receiving a reflection echo signal received by the ultrasonic probe; means  4  for re-constructing a form image according to the reception signal processed by the reception processing means; means  5  for re-constructing an elasticity image according to the reception signal processed by the reception processing means; means  7  for displaying the form image and the elasticity image; means  8  for switching between the form image mode and elasticity image mode; and means  9  for performing control so as to selectively acquire the form image and the elasticity image in the measurement period of the elasticity image mode switched by the mode switching means. Thus, it is possible to perform measurement associated with acquisition of both the form image and the elasticity image of the biological tissue and improve the image quality of the form image such as a B mode image and the image quality of the elasticity image such as elasticity ratio and elasticity distortion.

TECHNICAL FIELD

The present invention relates to a biological tissue elasticitymeasurement method and ultrasonographic apparatus, and, in particular,to a measurement method and ultrasonographic apparatus for acquiring ahigh quality elasticity image such as an elasticity ratio and anelasticity distortion of the biological tissue of a patient and a highquality form image of the biological tissue.

BACKGROUND ART

An ultrasonographic apparatus irradiates an ultrasonic wave to thepatient by using an ultrasonic probe, measures the acousticcharacteristic of a biological tissue within the patient by using thereflection echo signal, re-constructs a form image (such as a B-modeimage and an M-mode image) of the biological tissue, for example, basedon a difference or change in acoustic characteristic of an arbitraryarea of the patient and displays the form image on a screen for adiagnosis.

Recently, it has been proposed that the ultrasonographic apparatus isused to measure elasticity information including either elasticity ratioor elasticity distortion, for example, of a biological tissue of a partto be diagnosed and display it as an elasticity ratio image orelasticity distortion image (each of which will be generally calledelasticity image, hereinafter) (in Japanese Unexamined PatentApplication Publication No. JP/P2000-60853A, for example). According tothis, the form image of the biological tissue of the patient and theelasticity image such as the elasticity ratio and elasticity distortion,for example, are acquired simultaneously or alternately, and the formimage and the elasticity image are displayed in line or one over anotheron one screen.

However, the ultrasonographic apparatus disclosed in the publicationdoes not consider a measurement method for acquiring both high qualityform and elasticity images.

DISCLOSURE OF INVENTION

An ultrasonographic apparatus of the present invention includes anultrasonic probe for transmitting/receiving an ultrasonic wave to/from apatient, a unit for generating an ultrasonic transmission signal andtransmitting it to the ultrasonic probe, a unit for performing receptionprocessing on a reflection echo signal received by the ultrasonic probe,a unit for re-constructing a form image according to the receptionsignal processed by the reception processing unit, a unit forre-constructing an elasticity image according to the reception signalprocessed by the reception processing unit, a unit for displaying theform image and the elasticity image, a unit for switching between theform image mode and the elasticity image mode, and a unit for performingcontrol so as to selectively acquire the form image and the elasticityimage in the measurement period of the elasticity image mode switched bythe mode switching unit.

Thus, both of high quality form and elasticity images can be acquiredsince, according to the present invention, the unit is provided forperforming control so as to selectively acquire the form image and theelasticity image in the measurement period of the elasticity image modeswitched by the mode switching unit, that is, in the measurement periodof the elasticity diagnosis mode.

In this case, an ultrasonic transmission signal is applied which has anamplitude, wave number or frequency preferable for each of the formimage measurement and the elasticity image measurement as the ultrasonictransmission signal for each of the measurement. More specifically,there may be provided a first transmission signal generating unit forgenerating an ultrasonic transmission signal for the form image, and asecond transmission signal generating unit for generating an ultrasonictransmission signal for the elasticity image having at least oneultrasonic wave among an ultrasonic wave having a larger amplitude, anultrasonic wave having a larger wave number and an ultrasonic wavehaving a lower frequency than those of the ultrasonic transmissionsignal for the form image. As a result, the image quality of the formimage such as a B-mode image and the quality of the elasticity imagesuch as an elasticity ratio and an elasticity distortion can beimproved, and images suitable for both of the diagnoses can be provided.

The control unit may switch between the form image re-construction unitand the elasticity image re-construction unit according to the selectionof the form image or the elasticity image. Also, the control unit mayswitch between the first transmission signal generating unit and thesecond transmission signal generating unit.

The reception processing unit may have a first reception processing unitfor the form image for performing processing with a dynamic filterhaving a filter characteristic dependent on the depth of the reflectionecho signal, and a second reception processing unit for the elasticityimage for performing processing with a filter having a constant filtercharacteristic independent of the depth of the reflection echo signal.In this case, the control unit may switch between the first receptionprocessing unit and the second reception processing unit according tothe selection of the form image or the elasticity image.

The control unit can perform the switching for each frame of each imageor for each ultrasonic beam to be irradiated to a patient according tothe selection of the form image or the elasticity image. For example,when a focus area of elasticity image measurement is defined, thecontrol unit may switch the control for each ultrasonic beam to beirradiated to the patient and cause the ultrasonic beam to scan. In thiscase, the elasticity image re-construction unit may re-construct theelasticity image of the focus area and display it over the form image ona display unit. The display unit can be configured to selectivelydisplay one image of a form image and an elasticity image, an imagehaving both of them one over another, and an image having both of themin line.

A method for measuring an elasticity of a biological tissue of thepresent invention includes the steps of generating an ultrasonictransmission signal and transmitting it to an ultrasonic probe,performing reception processing on a reflection echo signal received bythe ultrasonic probe, re-constructing at least one of a form image andan elasticity image according to the reception signal having undergonethe reception processing, displaying at least one of the form image andthe elasticity image, switching between a form image mode and anelasticity image mode, and controlling so as to selectively acquire theform image and the elasticity image in the measurement period of theelasticity image mode switched by the step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block construction diagram of an embodiment of anultrasonographic apparatus of the present invention.

FIG. 2 is a diagram showing a relationship between the ultrasonographicapparatus of the present invention and a patient.

FIGS. 3 to 5 are diagrams showing an operation of a first embodiment ofthe present invention.

FIGS. 6 to 9 are diagrams for explaining an operation of a secondembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below withreference to attached drawings. FIG. 1 is a block construction diagramof one embodiment of an ultrasonographic apparatus of the presentinvention. In FIG. 1, the thick line indicates a flow of an ultrasonictransmission/reception signal, and the thin line indicates a flow of acontrol signal. FIG. 2 is a diagram showing a relationship between theultrasonographic apparatus according to this embodiment and a patient.As shown in FIG. 2, a patient 20 is laid on a bed 21, and measurement isperformed thereon by using an ultrasonic probe 1 in contact with thebody surface of the patient 20. In order to measure an elasticity image,an organ, for example, of the patient 20 can be pressed by theultrasonic probe 1. The ultrasonic probe 1 and the ultrasonographicapparatus 10 are connected via a probe cable. A form image 7 a and anelasticity image 7 b, for example, are displayed simultaneously on animage display device 7 of the ultrasonographic apparatus 10.

The ultrasonographic apparatus 10 includes a transmission circuit system2 and reception circuit system 3 connected to the ultrasonic probe 1 anda form image re-construction section 4 and elasticity imagere-construction section 5, to which a reception signal output from thereception circuit system 3 is transmitted. Data of form and elasticityimages re-constructed by the form image re-construction section 4 andelasticity image re-construction section 5 are input to a displaysuperimposing section 6. Image data formed by the display superimposingsection 6 is input to the image display device 7 and is displayed on thedisplay screen. A measurement control section 9 is configured to controlthe transmission circuit system 2, reception circuit system 3, formimage re-construction section 4, elasticity image re-constructionsection 5 and display superimposing section 6 based on a command inputfrom a switch 8 provided in the ultrasonic probe 1.

The ultrasonic probe 1 transmits/receives an ultrasonic wave to/from ameasurement target part of the patient 20. In other words, theultrasonic probe 1 has multiple transducers, which are alignedone-dimensionally or two-dimensionally, and has functions oftransmitting an ultrasonic wave to the inside of the patient 20 andreceiving an ultrasonic reflection echo wave from the inside of thepatient 20.

The transmission circuit system 2 is a transmission unit fortransmitting an ultrasonic signal having undergone transmission focusprocessing for giving a different delay time to each channel in drivingthe multiple transducers included in the ultrasonic probe 1 andtransmitting ultrasonic waves to multiple channels. In the transmissioncircuit system 2, an optimum transmission focus processing for each ofthem according to a form image or an elasticity image can be switched inaccordance with timing defined by the measurement control section 9,which will be described later. In particular, the transmission circuitsystem 2 has a transmission signal generating unit for generating anultrasonic transmission signal for a form image and a transmissionsignal generating unit for generating an ultrasonic transmission signalfor an elasticity image having at least one ultrasonic wave ofultrasonic waves having a larger amplitude, a higher wave number and alower frequency than those of an ultrasonic transmission signal for aform image. The transmission signal generating units for form andelasticity images are switched for use based on a command from themeasurement control section 9.

The reception circuit system 3 is a reception processing unit forperforming processing for receiving a reflection echo signal output fromthe ultrasonic probe 1, and performs amplification processing andfiltering processing and includes a phasing unit for performingreception focus processing. As well known, the reception focusprocessing captures reflection echo signals of multiple channelsreceived by the multiple transducers of the ultrasonic probe 1 and givesa different delay time to each of the channels to perform the receptionfocus processing, that is, phasing processing. Especially, in thereception circuit system 3 according to this embodiment, switching tooptimum reception focus processing for each of them according to a formimage or an elasticity image can be performed in accordance with timingdefined by the measurement control section 9, which will be describedlater. In particular, the reception circuit system 3 has a receptionprocessing unit for a form image for performing processing by using adynamic filter having a filter characteristic dependent on the depth ofa reflection echo signal and a reception processing unit for anelasticity image for performing processing by using a filter having aconstant filter characteristic independent of the depth of a reflectionecho signal. The reception processing units for form and elasticityimages are switched for use based on a command from the measurementcontrol portion 9.

The form image re-construction section 4 performs various kinds ofcomputing processing on a reception signal output from the receptioncircuit system 3 and creates and outputs a form image to the displaysuperimposing section 6. In other words, the form image-reconstructionsection 4 re-constructs a form image such as a B-mode image based on areception signal output from the reception circuit system 3. Accordingto this embodiment, a form image is re-constructed by using an outputfrom the reception circuit system 3 within a form image acquirementperiod defined by the measurement control section 9, which will bedescribed later.

The elasticity image re-construction section 5 performs various kinds ofcomputing processing on a reception signal output from the receptioncircuit system 3 and creates and outputs an elasticity image to thedisplay superimposing section 6. In other words, the elasticity imagere-construction section 5 stores a reception signal output from thereception circuit system 4 in a frame memory, for example, performscorrelation processing on two reception signals received after a timeinterval and obtains an amount of displacement of a biological tissue.An elasticity ratio or elasticity distortion of each part is obtained byperforming differentiation on the obtained amount of displacement, andan elasticity image thereof is re-constructed. The obtained elasticityimage is displayed on the image display device 7 through the displaysuperimposing section 6. In this embodiment, an elasticity image isre-constructed by using an output from the reception circuit system 3within an elasticity image acquirement period defined by the measurementcontrol section 9, which will be described later.

The display superimposing section 6 processes image such that outputsfrom the form image re-construction section 4 and the elasticity imagere-construction section 5 can be displayed one over another orselectively or separately and be output to the image display device 7 todisplay. In particular, in this embodiment, the methods for displayingon the image display device 7 are switched based on a command from themeasurement control section 9. The image display device 7 includes ageneral CRT monitor, for example.

The measurement control section 9 is configured to control each of theimplementation of elasticity image measurement for acquiring anelasticity image and the implementation of form image measurement foracquiring a form image. In other words, the measurement control section9 switches between the elasticity image measurement and the form imagemeasurement based on start and end commands for the elasticity diagnosismode, which are input from the switch 8 associated with the ultrasonicprobe 1. The switching is performed by controlling operations of thetransmission circuit system 2, reception circuit system 3, form imagere-construction section 4, elasticity image re-construction section 5and display superimposing section 6. A human interface device such as aswitch provided in the ultrasonographic apparatus 10 in FIG. 2, a footswitch, not shown, and a key board may be used instead of the switch 8,or together with the switch 8.

Here, the first embodiment relating to control of the elasticitydiagnosis mode to be performed by the measurement control section 9 willbe described with reference to FIGS. 3 to 5. When an operator pressesand turns on the switch 8 associated with the ultrasonic probe 1 inorder to start an elasticity diagnosis, this is input to the measurementcontrol section 9 as an elasticity diagnosis mode start command. Whenthe switch 8 is released and turned off, this is input to themeasurement control section 9 as an elasticity diagnosis mode endcommand. Based on this, the measurement control section 9 controls thestarting and ending of the elasticity diagnosis mode for performing acompound measurement of the elasticity image measurement and the formimage measurement. On the other hand, in the elasticity diagnosis mode,the operator must perform an operation for pressing the ultrasonic probe1 against the patient when the switch 8 associated with the ultrasonicprobe 1 is turned on. Conversely, when the ultrasonic probe 1 is pressedagainst the patient in advance, the operator must perform an operationof lifting the ultrasonic probe 1 when the switch 8 is turned on. Whilethe case that the operator directly performs the pressing of theultrasonic probe 1 will be described here, the ultrasonic probe 1 may bemechanically pressed or lifted. In this case, the ultrasonic probe 1 maybe pressed against the patient or the ultrasonic probe 1 pressed againstthe patient in advance may be lifted by using a machine for pressingdown the ultrasonic probe 1 though the additionally prepared humaninterface device such as the switch 8. Furthermore, the starting andending of the elasticity diagnosis mode may be controlled.

When the elasticity diagnosis mode start command is input, themeasurement control section 9 controls the switching of the componentsto selectively measure the form image and the elasticity image until theend command is input, that is, in the period of the elasticity diagnosismode. For example, as shown in FIG. 3, a sector measurement area (regionof interesting) of the elasticity image 33 is defined in a sectormeasurement area of the form image 32 here. In the figure, B-start andB-end indicate a scanning start position of the form image measurementand scanning end position of the form image measurement, respectively.The scanning with an ultrasonic beam is performed in the directionindicated by the shown arrow 31. S-start and S-end indicates a scanningstart position of the elasticity image measurement and scanning endposition of the elasticity image measurement, respectively. In thefigure, B corresponds to the form image measurement, and S correspondsto the elasticity image measurement.

A timing chart for an operation of the measurement control section 9 foracquiring an image as shown in FIG. 3 is shown in FIG. 4. In the figure,changes in operational states of the “switch (8)”, “ultrasonic scanningposition”, “transmission/reception sequence”, “ultrasonic transmissionwave number(s)” and “reception of ultrasonic waves” are shown in orderfrom the top of the figure. The horizontal axis indicates the number oftimes of scanning; B corresponds to the form image measurement; Scorresponds to the elasticity image measurement; and the subscripts sand e indicate the start and the end, respectively.

When the operator presses and turns on the switch 8 of the ultrasonicprobe 1, the measurement control portion 9 starts measurement control ofthe elasticity diagnosis mode based on the timing chart in FIG. 4 and aflowchart shown in FIG. 5. In this embodiment, thetransmission/reception sequence B of the form image measurement and thetransmission/reception sequence S of the elasticity image measurementare switched and implemented by following predefined steps for eachimage frame, for example, in the period of the elasticity diagnosis modewhen the switch 8 is kept on. In other words, each of the scanning fromB-start to B-end and the scanning from S-start to S-end is handled as aunit for switching and implementation. In the shown example, after theform image measurement B is performed for one frame, the elasticityimage measurement S is implemented for one frame. Then, after the formimage measurement B is implemented for two frames, the elasticity imagemeasurement S is implemented for one frame. However, the presentinvention is not limited to the ratio of the repetition in FIG. 4.

The measurement control section 9 switches and controls the transmissioncircuit system 2, the reception circuit system 3, the form imagere-construction section 4, the elasticity image re-construction section5 and the display superimposing section 6 based on the timing chart.First of all, when the elasticity diagnosis mode is started, theposition of a predefined focus area for measuring the elasticity image33 is captured. Then, the starting position (S-start) and endingposition (S-end) of the elasticity image measurement are defined for thefocus area. Next, the scanning for the form image measurement is startedbased on the timing chart in FIG. 4. At that time, a command forswitching to an ultrasonic transmission signal (one-wave transmission inthe example in FIG. 4) suitable for the form image measurement is outputto the transmission circuit system 2. Moreover, a command for switchingto reception processing with the dynamic filter is output to thereception circuit system 3, and a command for re-constructing the formimage based on an input reception signal is output to the form imagere-construction section 4. Thus, when the scanning of the form imagemeasurement completes once, the processing is switched to the elasticityimage measurement. The switching outputs a command for switching to anultrasonic transmission signal (two-wave transmission in the example inFIG. 4) suitable for the elasticity image measurement to thetransmission circuit system 2. Furthermore, a command for switching toreception processing with the fixed filter is output to the receptioncircuit system 3, and a command for re-constructing an elasticity imagebased on an input reception signal is output to the elasticity imagere-construction section 5. However, the actual scanning for theelasticity image measurement is performed during the period from theS-start to S-end in FIG. 3. Thus, as shown in FIG. 4, thetransmission/reception sequence is selected and implemented in order ofB-S-B-B-S-B-B . . . . The elasticity image re-construction section 5obtains an amount of displacement of a biological tissue by performingcorrelation processing on two reception signals having a time interval,which are obtained by the second and fifth scanning in FIG. 4, obtainsan elasticity ratio or elasticity distortion based on the obtainedamount of displacement and re-constructs the elasticity image. In thisway, since the scanning of the form image measurement is performed twiceduring two measurement scans required for the elasticity imagemeasurement, the amount of displacement of a biological tissue increasesduring the period. Therefore, the precision of measurement of anelasticity ratio or the like can be enhanced.

On the other hand, the measurement control portion 9 controls thedisplay super imposing circuit 6 to cause the image display device 7 toselectively display the form image and the elasticity image newlycreated by the form image re-construction section 4 and the elasticityimage re-construction section 5. A frame memory for storing are-constructed image is provided in each of the form imagere-construction section 4 and the elasticity image re-constructionsection 5. In order to perform the display control over the form imageand the elasticity image, the measurement control section 9 does notinput a reception signal for the elasticity image, which has undergonephasing processing in the reception circuit system 3, to the form imagere-construction section 4 during the period for acquiring the elasticityimage data but controls outputs to cause the image display device 7 todisplay the form image using the form image data, which is previouslyacquired and stored in the frame memory, during the period. Theelasticity image re-construction section 5 is commanded not to capture areception signal for a form image, which has undergone phasingprocessing in the reception circuit system 3 during the period foracquiring the form image data, and outputs are controlled to cause theimage display device 7 to display the elasticity image using theelasticity image data, which is previously obtained and stored in theframe memory, during the period. Thus, in the form image measurement andelasticity image measurement, optimum transmission and receptionprocessing for each of them is performed. Then, when the switch 8 isturned off, the measurement for the elasticity diagnosis mode ends.Notably, until the switch 8 is turned on again, control can be performedto repeat the form image measurement and display the latest form imageon the image display device 7 and to display a previously acquiredelasticity image on the image display device 7 as the elasticity image.

The control operation by the measurement control section 9 forimplementing measurement control shown in the timing chart in FIG. 4will be described by using the flowchart shown in FIG. 5. First of all,in step S51, whether the ultrasonic scanning is to be ended or not isdetermined. If not (No), the processing moves to step S52. If so (yes),ultrasonic scanning processing ends immediately.

In step S52, whether the current period is the period for elasticityimage measurement, that is, for the elasticity image measurement S ornot is determined. If yes, the processing moves to step S58. If no, theprocessing moves to step S53. B-start is stored in the form imageacquirement position register in step S53 in order to start theacquirement of the form image since it is determined in previous stepS52 that the current period is not the period for the elasticity imagemeasurement S. In step S54, whether the value of the form imageacquirement position register is B-end, that is, the final form imageacquirement position or not is determined. If the determination resultsin yes, the processing moves to step S57 where the acquirement of theform image data ends. Then, the processing returns to step S51. If thedetermination results in no, the processing moves to step S55. In stepS55, the value of the form image acquirement position resister isincremented by 1. In other words, the ultrasonic beam line address isshifted by one in the direction of scanning. In step S56, one-wavetransmission, for example, is performed thereon with an ultrasonictransmission signal for the form image measurement. Furthermore,reception signal processing by using a dynamic filter is performedthereon, and the form image measurement is implemented. Then, theprocessing returns to step S54. In this way, by performing receptionsignal processing by using a dynamic filter, the reception frequency canbe adjusted according to the depth of reception so that ultrasonictransmission/reception suitable for the form image acquirement can beperformed. The processing in steps S54 to S56 can scan the form image 32in the scanning direction 31 from the position B-start, and the formimage 32 to the position B-end can be acquired.

In step S58, S-start is stored in the elasticity image acquiringposition register to start elasticity image measurement since it isdetermined in previous step S52 that the current time is in the periodof the elastic image acquiring time (S). In step S59, whether the valueof the elasticity image acquiring position register is S-end or not,that is, whether it indicates the last acquiring position of theelasticity image or not is determined. If the determination results inyes, the processing moves to step S5C where the acquirement of theelasticity image data ends. Then, the processing returns to step S51. Ifno, the processing moves to step S5A. In step S5A, the value of theelasticity image acquiring position register is incremented by 1. Thatis, the ultrasonic beam line address is shifted by one in the scanningdirection. In step S5B, two-wave transmission and reception signalprocessing using a fixed filter are performed, for example, with anultrasonic transmission signal for elasticity image measurement so thatthe elasticity image acquiring processing by elasticity imagemeasurement can be implemented. Then, the processing returns to stepS59. By performing the two-wave transmission, ultrasonic transmissionsuitable for elasticity image measurement is performed. By performingultrasonic reception by using a fixed filter, ultrasonictransmission/reception suitable for elasticity image acquirement can beperformed with a constant reception frequency. The processing in stepsS59 to S5B scans the elasticity image 33 in the scanning direction 31from the position S-start, and the elasticity image 33 to the positionS-end can be acquired. In the example in FIG. 3, an affected part 34 isdisplayed in the elasticity image 33. Upon completion of the acquirementof the elasticity image 33, the determination in step S51 is performedagain, and the processing for acquiring the form image 32 or elasticityimage 33 is performed according to the result. When an operator releases(switches off) the switch 8, the processing is shifted to a processingoperation in an independent measurement mode for acquiring a form imageuntil the switch 8 is pressed again.

The form image measurement and elasticity image measurement can beperformed under each independent and proper ultrasonic transmissionrequirement since the transmission circuit system 2 includes, like theabove-described embodiment, the transmission signal generating unit forgenerating an ultrasonic transmission signal for a form image and thetransmission signal generating unit for generating an ultrasonictransmission signal for an elasticity image having a larger wave numberthan that of the ultrasonic transmission signal for a form image. As aresult, ultrasonic images optimum for both form image and elasticityimage can be re-constructed and displayed, and images suitable for adiagnosis can be provided to an operator. The image quality can beimproved by selectively controlling the form image measurement andelasticity image measurement in the period of the elasticity diagnosismode.

The quality of a form image can be further enhanced since the receptioncircuit system 3 includes and switches between a form image receptionprocessing unit for processing with a dynamic filter having a filtercharacteristic (frequency characteristic) dependent on the depth of areflection echo signal and an elasticity image reception processing unitfor processing with a filter having a constant filter characteristicindependent of the depth of a reflection echo signal.

While the case that the signal strength of a reception signal relatingto an elasticity image is increased by using an ultrasonic transmissionsignal with a higher wave number in acquiring elasticity image data hasbeen described in the above-described first embodiment, ultrasonictransmission with a large amplitude may be used instead. Alternatively,an ultrasonic transmission signal with a low frequency (10 MHz for formimage measurement and 7.5 MHz for elasticity image measurement) may beused. Alternatively, a combination of an ultrasonic wave with a largewave number, an ultrasonic wave with a high amplitude and an ultrasonicwave having a low frequency may be used as required. That is, since theamount of displacement of a biological tissue is generally small, anultrasonic wave with a larger amplitude or a larger wave number or anultrasonic wave with a lower frequency than that of the ultrasonic wavefor acquiring a form image is desirably used in order to increase theprecision of the detection of a particularly hard part. Conversely, themeasurement for acquiring a form image by an ultrasonic wave with alarge amplitude results in an excessively large ultrasonic receptionsignal, or the measurement by an ultrasonic wave with a large wavenumber results in a decrease in distance resolution.

Next, a second embodiment relating to control of an elasticity diagnosismode to be performed by the measurement control section 9 will bedescribed with reference to FIGS. 6 to 9. FIG. 6 is a timing chart of anoperation. FIGS. 7 to 9 are flowcharts illustrating details of theoperation. FIG. 6 shows, like FIG. 4, changes in states of “switch (8)”,“ultrasonic scanning position”, “transmission/reception sequence”,“ultrasonic transmission wave number(s)” and “reception of ultrasonicwaves” in order from the top of the figure. The horizontal axisindicates the number of times of scanning, and DF and FF indicate adynamic filter and a fixed filter, respectively. The meaning of theother symbols is identical to those of FIG. 4. This embodiment isdifferent from FIG. 4 in that the form image measurement and elasticityimage measurement are selectively switched not for each image frame butfor each ultrasonic beam.

As shown in FIG. 6, during form image measurement B, an ultrasonictransmission signal with one wave number is output from the transmissioncircuit system 2, and reception processing is implemented by using adynamic filter (DF) in the reception circuit system 3. On the otherhand, during elasticity image measurement S, an ultrasonic transmissionsignal with two wave numbers is output from the transmission circuitsystem 2, and reception processing is implemented by using the fixedfilter (FF) in the reception circuit system 3. Thus, for the form imagemeasurement and elasticity image measurement, transmission and receptionprocessing optimum for the image processing thereof can be implemented.

The measurement control section 9 repeatedly implements elasticity imagemeasurement and form image measurement with different ultrasonic beamscanning positions in the elasticity image measurement S and form imagemeasurement B. The elasticity image re-construction section 5 obtains anamount of displacement of a biological tissue by performing correlationprocessing on two reception signals having a time interval, which areobtained by the first and nth scanning in FIG. 6, obtains an elasticityratio or elasticity distortion based on the obtained amount ofdisplacement and re-constructs an elasticity image. When the measurementin the elasticity diagnosis mode ends based on a command from the switch8, the measurement control section 9 controls to acquire form image dataand to display a previously obtained and displayed elasticity image andthe latest form image on the image display device 7.

Furthermore, the details will be described by following the flowchartsshown in FIGS. 7 to 9. When an operator presses and switches on theswitch 8 of the ultrasonic probe 1, ultrasonic scanning start processingin FIG. 7 is started. Then, in step S71, whether ultrasonic scanning hasended or not is determined. If not (no), the processing moves to stepS72. If so (yes), the ultrasonic scanning processing ends immediately.

In step S72, whether the value of the current scanning position registeris the position equal to or higher than B-start and lower than S-startor not is determined. If yes, the processing moves to step S73. If no,the processing moves to next step S74. In step S73, a form imageacquirement routine in FIG. 8 is implemented. The form image acquirementroutine performs one-wave transmission, for example, with an ultrasonictransmission signal suitable for the form image measurement mode,performs reception signal processing by using a dynamic filter,implements form image acquirement processing in the form imagemeasurement mode, increments the value of the scanning position registerby 1 only and returns to step S71 in FIG. 7. The form image acquirementroutine in step S73 is implemented to acquire form image data until thevalue of the scanning position register reaches S-start from B-startthereafter.

In step S74, whether the value of the current scanning position registeris the position equal to or higher than S-start and is equal to or lowerthan S-end or not is determined. If yes, the processing moves to stepS75. If no, the processing moves to next step S76. In step S75, anelasticity image/form image acquirement routine in FIG. 9 isimplemented. The elasticity image/form image acquirement routinerepeatedly implements an operation including acquiring elasticity data,implementing acquirement of form image data after the acquirement,performs elasticity image scanning again after a predetermined interval.That is, compound measurement is implemented on the area of the formimage 33 corresponding to a focus area by switching between the formimage measurement mode and the elasticity image measurement mode foreach ultrasonic beam line address. In the elasticity image/form imageacquirement routine, two-wave transmission is performed, for example,with an ultrasonic transmission signal suitable for the elasticity imagemeasurement, and processing of a reception signal uses a fixed filter.One-wave transmission is performed, for example, with an ultrasonictransmission signal suitable for the form image measurement, andprocessing of a reception signal implements processing using a dynamicfilter. Next, the value of the scanning position register is incrementedby 1 only, and the processing returns to step S71 in FIG. 7. Theelasticity image/form image acquirement routine in step S75 isimplemented, and the scanning of a form image and the scanning of anelasticity image are alternately repeated to acquire the image until thevalue of the scanning position register reaches S-end from S-startthereafter.

In step S76, whether the value of the current scanning position registeris a position higher than S-end and equal to or lower than B-end or notis determined. If yes, the processing moves to step S77. If no, theprocessing returns to step S71. That is, after the elasticity imagescanning to the position S-end ends, the form image data acquirement isrepeated up to the position B-end. In step S77, a form image acquirementroutine in FIG. 8 is implemented. The form image acquirement routineperforms one-wave transmission, for example, with an ultrasonictransmission signal suitable for form image measurement, implementsreception processing using a dynamic filter, increments the value of thescanning position register by 1 only and returns to step S71 in FIG. 7.The form image acquirement routine in step S77 is implemented to acquirethe form image 32 until the value of the scanning position registerreaches S-start from S-end thereafter.

Then, the form image data acquirement is performed from B-start to B-enduntil an operator presses the switch 8 again. When the operator pressesthe switch 8 again, the processing returns to the beginning, and aseries of operations from the form image scanning from the positionB-start is repeated.

As described above, according to the second embodiment, the sameadvantages as those of the first embodiment can be obtained.

1. An ultrasonographic apparatus, comprising: an ultrasonic probe fortransmitting/receiving an ultrasonic wave to/from a patient; means forgenerating an ultrasonic transmission signal and transmitting it to theultrasonic probe; means for performing reception processing on areflection echo signal received by the ultrasonic probe; means forre-constructing a form image according to the reception signal processedby the reception processing means; means for re-constructing anelasticity image according to the reception signal processed by thereception processing means; means for displaying the form image and theelasticity image; means for switching between the form image mode andthe elasticity image mode; and wherein the reception processing meansincludes first reception processing means for the form image and secondreception processing means for the elasticity image; and means forcontrol between the first processing means and the second processingmeans; wherein the control means switches between the first receptionprocessing means and the second reception processing means according toselection of the form image and the elasticity image.
 2. Theultrasonographic apparatus according to claim 1, wherein the controlmeans switches between the form image re-construction means and theelasticity image re-construction means according to the selection of theform image or the elasticity image.
 3. The ultrasonographic apparatusaccording to claim 1, wherein the transmission means has firsttransmission signal generating means for generating an ultrasonictransmission signal for the form image; and second transmission signalgenerating means for generating an ultrasonic transmission signal forthe elasticity image having at least one ultrasonic wave among anultrasonic wave having a larger amplitude, an ultrasonic wave having alarger wave number and an ultrasonic wave having a lower frequency thanthose of the ultrasonic transmission signal for the form image.
 4. Theultrasonographic apparatus according to claim 3, wherein the controlmeans switches between the first transmission signal generating meansand the second transmission signal generating means according to theselection of the form image or the elasticity image.
 5. Theultrasonographic apparatus according to claim 1, wherein: the firstreception processing means performs processing with a dynamic filterhaving a filter characteristic dependent on the depth of the reflectionecho signal; and the second reception processing means performsprocessing with a filter having a constant filter characteristicindependent of the depth of the reflection echo signal.
 6. Theultrasonographic apparatus according to claim 1, wherein the controlmeans performs control, for each frame of each image, so as toselectively acquire the form image and the elasticity image.
 7. Theultrasonographic apparatus according to claim 1, wherein the controlmeans performs control, for each ultrasonic beam to be irradiated to thepatient, so as to selectively acquire the form image and the elasticityimage.
 8. The ultrasonographic apparatus according to claim 1, whereinthe control means switches, for each ultrasonic beam to be irradiated tothe patient, control for selectively acquiring the form image and theelasticity image with respect to a defined focus area and causes theultrasonic beam to scan; and the elasticity image re-construction meansre-constructs the elasticity image of the focus area and displays itover the form image on the display means.
 9. The ultrasonographicapparatus according to claim 1, wherein the control means switches, foreach frame of each image or for each ultrasonic beam to be irradiated tothe patient, control for selectively acquiring the form image and theelasticity image during the period from the time when a measurementstart command of the elasticity image mode is input from the modeswitching means to the time when a measurement end command is inputtherefrom.
 10. The ultrasonographic apparatus according to claim 1,wherein the display means selectively displays one image of the formimage and the elasticity image, an image having both of them one overanother and an image having both of the in line.
 11. Theultrasonographic apparatus according to claim 1, wherein the modeswitching means is at least one of human interface equipment such as aswitch provided in the ultrasonic probe, a switch provided in theapparatus body, a foot switch and a keyboard.
 12. A method for measuringan elasticity of a biological tissue, comprising the steps of:generating an ultrasonic transmission signal and transmitting it to anultrasonic probe; performing a step of reception processing on areflection echo signal received by the ultrasonic probe by selectivelycontrolling switching between a first reception mode and a secondreception mode; re-constructing a form image and an elasticity imagebased on the reception signal having undergone the reception processing;displaying at least one of the form image and the elasticity image; andswitching between a form image mode and an elasticity image mode;wherein the reception processing step switches between and performsfirst reception processing for the form image and second receptionprocessing for the elasticity image according to the selection of theform image and the elasticity image.
 13. The biological tissueelasticity measurement method according to claim 12, wherein theultrasonic transmission signal for the elasticity image generated by thetransmission step has at least one ultrasonic wave among an ultrasonicwave having a larger amplitude, an ultrasonic wave having a larger wavenumber and an ultrasonic wave having a lower frequency than those of theultrasonic transmission signal for the form image.
 14. The biologicaltissue elasticity measurement method according to claim 12 or 13,wherein the first reception processing is for performing processing witha dynamic filter having a filter characteristic dependent on the depthof the reflection echo signal and the second reception processing is forperforming processing with a filter having a constant filtercharacteristic independent of the depth of the reflection echo signal.15. The biological tissue elasticity measurement method according toclaim 12, wherein the control step switches, for each frame of eachimage, between the ultrasonic transmission signals for the form imagemeasurement and the elasticity image measurement.
 16. The biologicaltissue elasticity measurement method according to claim 12, wherein thecontrol step switches, for each ultrasonic beam to be irradiated to thepatient, between the ultrasonic transmission signals for the form imagemeasurement and the elasticity image measurement.
 17. The biologicaltissue elasticity measurement method according to claim 12, wherein thecontrol step scans an ultrasonic beam by the ultrasonic transmissionsignal for the elasticity image measurement with respect to a definedfocus area; and the image re-construction step re-constructs theelasticity image of the focus area and displays it over the form imageon the display means.
 18. The biological tissue elasticity measurementmethod according to claim 12, wherein the control step switches, foreach frame of each image or for each ultrasonic beam to be irradiated tothe patient, control for selectively acquiring the form image and theelasticity image during the period from the time when a measurementstart command of the elasticity image mode is input to the time when ameasurement end command is input.
 19. The biological tissue elasticitymeasurement method according to claim 12, wherein the measurement startand end commands of the elasticity image mode are input from at leastone of human interface equipment such as a switch provided in theultrasonic probe, a switch provided in the apparatus body, a foot switchand a keyboard.